Crystal diodes and joint contact device



Oct. 2, 1951 H. F. MATARE ETAL CRYSTAL DIODES AND JOINT CONTACT DEVICE Filed Feb. 16. 1949 Patented Oct. 2, 1951 'HerBcrt-JFrancoisMatar I eGiargan, Franceyassignors to edite: Compagnie des Freins e, Paris, France vaucresson and Andr tinghqus *Kppllca't'ion mastery 16, 1949, Serial No. "76.8.52 In FraficeFebruary 18, 1948 This invention; rela-tcsto: crystal; diodes, and more especially to, contact devicesqadapted ;for use in establishing-point contactwith the crystal. .;-I;tis:an.obiect f-this invention to provide-means for,- improvingtthis;contact-by fitting crystaldioides .Witha control device superior in: many respects toihosehithertoinzuse. 4 l I ,The-greatestproblem-presented in the use of these diodesis presented; by the so-called- -o'ontflctineedlcfi ayerythin wire called; upon to estabpoint; contact; with the crystal under an exactly predetermined pressure. M I The needles hitherto. us ed;--have been in the form of. thespringmoilscapable of absorbing shocks: or; vibrations; which occur duringuse while applying the necessary amountgiot pressure.tainsum: permanent" contact. of necessity, such a springcoil mustbe-as small; asipossible in order to minimize the forces tendingzto produce. a. dis.- placement of the contact crystal oraninterruptionof contact as by a. lifting of the needle point therefrom.

; q z erafiq se u the c n es th c nt m nte h cr ta s it as been rqposatqc nrqlihe-snr ns- 11 e1 PEQ E Q 1161 0 possible which, of course. causes reduction in theirela'sticity. I The contact device according. to. the present invention avoids n1 these drawbacks by solving the a considerable problem from altogether different anglawhile at the same. time ensuring their ready volume production, to provide bonta'ct devices of-3remarkable uniformity in mechanical properties and which eliminate the greater part of electrical ses r nduqtanee....., In the contact device according liq. this invenli ns l me b r h t establ s es c pa co tact has the fo m r, a. step 1g cylindrical cap or ca 'suietne basic form of which is. a pointed cone,

on the. surface of the .40 been made to keep the needle wiresyas shortas The form and number of steps may, of course, vary according to the flexibility required. H In the drawings accompanying this specifica tion and forming a part thereof an embcicliinent of the invention is shown diagrammatically by way of example.

In the drawings: v p w Fig. 1 is an .elevat ional view partly in crosssection, of a diode equipped with the device according to this invention.

Fig. 2 "shows on a larger scale a vertical axial section of the cap, while Fig. 3 is a plan view. Fig. '4 is a diagrammatic torted condition. Fig. 5 is a plan view of a blank from which the cap may be made by stamping'orpressing'. Y i Figs. 6 and.7=are wiringdiagrams'of equivalent circuits respectively of-fa crystal diode :of a well known type in which the needle is formedzpot a mere spring and oi a crystal diodefitted with a resilient capsule according to the invention. The principle of the invention resides in the specific construction of the cap. As shown in view of the cap in dis- Figs. 1 and 2 ;the c ap is formed with three cylindrical portions 1, land 3 of-dec'ieasing diameters, the widest of which is welded to the end of an electrode 4. 5 is the point which is fitted centrally to the narrowest part 3 of the cap.

In rder to ncr ase. t e re il e cy i he a sule it may be formed of segments connected only at the-center, as shown in Fig. 5; where a blank of clover-leaf contour with four segments 6 separated by deep gaps 1 merge only in the bottom section is designed to have the point fixed to it. This blank, when pressed into capsule shape, will produce a softer elasticity than the closed form shown in Fig. 2.

The point may be made either separately and fixed by welding to the. cap, or v anietal deposit may be made on the center f the cap whichis subsequently ground into a pointed cone. This point-contact device offers the following advantages: E

It lends itself to volume-production on the largest scale. I

It provides for an automatic centering of great stability on the crystal.

It is substantially insensitive to mechanical shocks. H b

The inductance is reduced to" a minimum whereby the inherent frequency of the detector is substantially enhanced I In (order to better. illustrate, the invention a description will now be iven or the resiliency or elasticity problem in relation to a point contactsystem of this type, by comparing such resiliency with that of members utilized up to now for making the required point contact.

Where this contact action is obtained by means of a conventional cylindrical spring member (Fig. 1) the value of the deformation will be:

wherein d =amplitude of the deformation in cm. n=number of turns j r=radius d=wire thickness of diameter in cm. P=total pressure exerted in kg. G=torsion modulus in kg./cm.

If a platinum. spring is used, having the following characteristics:

then

(1]: will be =1.1 lcm. (2)

which form the successive steps of the membern Thus that is, in the case of a three-step capsule:

wherein:

d,,=value of the deformation in cm. P=total pressure exerted in kg. n=radius of the largest step =radiuses of the successive intermediate steps r,,=radius of the smallest step h=thickness of the plate or sheet used E =elasticity modulus in kg./cm..

By way of example, calculus will give, in accordance with the above formula, the deformation dp for a three-step capsule whose plates ail-1Q made of nickel of has the value dprsAn X 10 l This value is still greater if the elasticity modulus E is that of platinum or other highly elastic metal, which may of course also be used.

In the preceding Formula 3 the fact that dp corresponds to the maximum deformation in the middle of the plates has been tion. However this pensated for by the fact that the plates are not solid and their association actually forms a kind of funnel made of a succession of hollow cylinders the deformation of which will be higher than that calculated according to Formula 3.

In addition, it should be noted that walls will also be moved under the pressure exerted as illustrated in Fig. 4. The angle'u formed after the deformation by the side wall of themtermediate step or annular portion with the "general axis of the system will constitute an additional variable which will increase the initially found value of dp. The Formulae obtained by assuming a homogeneous pressure exe'rted'cen trally of the plates cannot be extended to the case where rz r1 or rarz,whichamounts tofsaying that the relations ri rand T2 T3 should be constantly observed. J

Considering all the capabilities of movement of the successive cylindrical envelopes theifollowing formula could be adopted:

This formula 'is applicable'to the deformation of an annular plate bearing freely through its periphery on a support and subjected to a uniformly distributed pressure from withina circumference having an average radius of 2T2.

Taking the same values as for thecalculation's effected with Formula 4 for the various elements in question, d will thus become;

This value is higher than that resulting from the application of Formula 4. Intact the actual result in practice lies between these two values while being closer to the latter value.

In any case, it will be'seen thatthe' value of the deformation does 'not substantially diifer from that obtained with a cylindrical spring. This is readily ascertained by comparing the re- Suits (2), (5) andi'l):

It should be noted however that the elasticity limit of the material employed will be always more rapid'y: reached when the construction utilizes the cup-shaped element wherein the tension 0' is calculated according to the formula:

=gqsl png) .025(3)? 651-182 kg/em. (9)

which is lower than normal values afforded nickel material.

It should furthermore-be observed that the values of E may be advantageously improved by the use of alloys which will permit a substantial.

kept in considera- V small error is largely comthe vertical reduction of the rather high pressure of 1 gr. taken in the above calculations, by analogy with cylindrical springs of the type shown in Fig. 1 which is the pressure value usually accepted for these springs while keeping the lip value substantially at the same level.

Side-displacements, due to mechanical shocks, the more detrimental of which would be those applying a, component force at right angles with the vertical or normal axis of the capsule, has a much smaller chance of occurring in this case. Consequently, no disadvantage secured if this pressure is further reduced while such reduction of the pressure at the same diminishes the electric capacity of contact between the point and crystal elements.

Comparing now the substitution or equivalent diagrammatic circuits shown in Figs 6 and 7 which correspond respectively to the prior art spring system and the elastic cup system according to the invention (Fig. '7) respectively, it should be noted that:

while setting down:

it will be apparent that a diode tube equipped with the contact member according to the present invention has electrical properties such that the energy of the hyperfrequencies is better concentrated at the limit or stopping layer D.

We claim:

1. A point-contact element for crystal diodes a hollow capsule of resilient material having the axial section of a low stepped cone.

2. The point-contact element for crystal diodes of claim 1 in which the capsule has the form of several cylindrical annuli of difierent diameters arranged in axial superposition, fiat annuli connecting the bottom edge of a larger with the top edge of a smaller cylindrical annulus, and a bottom closing the smallest cylindrical annulus.

3. A crystal diode comprising the point-contact device of claim 1.

4. A point contact element for crystal diodes comprising in combination, a hollow apertured capsule formed from a blank provided with radial slots and shaped with at least one step defining at least two cylindrical parts of different diameters and at least one annular part and a flat and central part connecting the lower edges of said cylindrical parts, a pointed member being fixed to fiat end central part.

HERBERT FRANCOIS MATARE'. ANDRE POILLEAUX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 689,199 Kinraide Dec. 17, 1901 FOREIGN PATENTS Number Country Date 78,069 Austria Sept. 10, 1919 

